The bulkhead of a gas turbine engine combustor must be protected from the radiant heat of the gas within the combustor. A bulkhead liner performs the function, but it must itself be cooled.
In addition to impingement cooling on the cold side conventional cooling uses inside to outside cooling flow. In other words, the cooling air flow passes radially outward, with respect to the fuel nozzle, from the fuel nozzle guide.
Where recirculating combustor flow is required passing from the combustor shell to the nozzle, the inside to outside cooling flow disrupts this recirculating flow. Therefore outside to inside flow is preferred. It also desirable to be able to easily replace any structure used to facilitate the desired cooling flow.